In recent years, following the requirements for downsizing of electronic appliances, downsizing, high integration and multi-functionalization of semiconductor devices to be used for the electronic appliances are being rapidly advanced, and a number of electrodes which connect a semiconductor device and an electronic appliance to each other tends to increase. As the semiconductor device to be used herein, those which have a wiring redistributed on a semiconductor pad formed of aluminum or the like and provided with a bump electrode are frequently used. In order to simultaneously cope with the downsizing of the semiconductor device and the increase of the electrode number as described above, there are proposed a variety of formation methods of a bump electrode (for example, Patent Documents 1 and 2).
In these formation methods of a bump electrode, there may be the case where an etching step of a wiring to be provided on a semiconductor pad (hereinafter also referred to merely as “electrode”) is present, and copper must be etched without etching nickel which is used for the wiring.
More specifically, the formation method of a bump electrode disclosed in Patent Document 1 includes a step of etching, in which on a substrate provided with an electrode which is constituted of an electrically conductive material, a cover film which is opened in the electrode portion is provided; a base electrically conductive film formed by sputtering copper or the like, a photoresist film having an opening extending from the electrode to an area on which a bump electrode is formed, and a copper wiring and a nickel wiring in the opening by electrolytic plating are successively provided; the photoresist film is then removed; and a portion of the base electrically conductive film, which is not covered by the wirings, is etched. In etching copper which forms the base electrically conductive film in the step of etching, in order to ensure higher performances, it is desirable that the nickel wiring formed by electrolytic plating is not etched.
Also, the formation method of a bump electrode disclosed in Patent Document 2 includes an etching step in which on a semiconductor substrate having an aluminum electrode provided therewith, a seed layer is formed of titanium or copper by means of sputtering; a resist in which a portion for forming a bump electrode is opened is formed; a barrier metal layer obtained by laminating plural metals such as titanium, copper, nickel, etc. is formed in the opened area by means of electrolytic plating or the like; solder working as a bump electrode is further formed thereon by means of electrolytic plating; the resist is then removed; and the seed layer is subsequently etched. In etching titanium or copper which forms the seed layer in the step of etching, in order to ensure higher performances, it is desirable that the metal which forms the barrier metal layer, such as nickel, etc., is not etched; and that at the same time, oxidation of the bump electrode composed of solder with an etchant is prevented from occurring, thereby suppressing a reduction of performances of the electrode.
But, in the etching step of Patent Document 1 or Patent Document 2, an etchant which is used in the subject step is not sufficiently reviewed, and in etching the member such as the wiring composed of copper, or the like, even the member composed of nickel is etched, too. Also, it is highly expected that the bump electrode is oxidized, whereby its performances are reduced. As described above, with the progress of downsizing, high integration and multi-functionalization of semiconductor devices, required performances by a customer who uses the semiconductor device are becoming severe. Then, in semiconductor devices which are manufactured by a conventional manufacturing method of semiconductor devices, the tendency that the case where the subject required performances cannot be sufficiently satisfied is caused has become remarkable.